If men who have prostate cancer do interval training three times a week for half an hour, the speed at which their illness develops declines dramatically. Danish sports scientists reported this in 2016 in Cancer Causes & Control.

Study
The Danes performed an experiment with 19 men who were being monitored closely by their doctors because they had prostate cancer. Some had had their prostate gland removed, others had not, and all of them had a raised PSA level. The higher your PSA level, the greater the chance that you have prostate cancer.

The seven men in the control group did nothing. The twelve men in the experimental group did a 35-minute interval training session three times a week. They were allowed to choose between running, rowing and cycling.

"The first week day of training, the training consisted of intervals of 5- to 10-min duration (intensity 55-75% of VO2max), the second day of intervals of 5- to 25-min duration (intensity 55-75% of VO2max), and the third day of intervals of 1- to 5-min duration (intensity 50-100% of VO2max)," the Danes wrote. [More about the training schedule]

The experiment lasted 24 months. The Danes examined the men just before they started the programme, after six months and again after 24 months.

Results
The men who trained became more muscular and lost weight.

The PSA Doubling Time [the time it took for the PSA level to double] increased dramatically in the men who trained, as the figure above shows. So the speed at which their illness developed slowed down. This did not happen to the men in the control group.

It appeared that the decrease in fat mass and increase in muscle mass made a slight contribution to the increase in PSA Doubling Time, but the effects were negligible. It was principally the increase in endurance capacity [for example the increase in VO2max] that extended the PSA Doubling Time – and delayed the development of the cancer.

Conclusion
"The exercise intervention resulted in marked physiological adaptations that aided weight regulation and increased fitness levels," Pernille Hojman who led the research team explained in an interview. [renalandurologynews.com November 25, 2015] "PSA doubling time correlated with improved fitness, but not with weight loss. These findings suggest there is a fitness component that plays a role in the control of prostate cancer that is not related to weight."

The researchers are more explicit in their publication. "The present study demonstrated a promising tendency toward improvement in PSA Doubling Time, adding some support to the idea that increased level of physical activity leading to improved fitness level may be a factor contributing to delay prostate cancer progression", they wrote.